Speed-control means for lifting mechanisms



June 10 1924. 1,497,091

E. F. DAHILL SPEED CONTRC JL MEANS FOR LIFTING MECHANISMS Filed Nov. 18 1922 2 Sheets-Sheet 1 W, ww

June 10 1924.

E. F. DAHILL SPEED CONTROL MEANS FOR LIFTING MECHANISMS Filed Nov. 18. 1922 2 Sheets-Sheet 2 1 vwentoz attorney Patented June 10, 1924;.

EDWARD IE. DAHILL, OF NEW BEDFORD, MASSACHUSETTS.

SPEED-CONTROL MEANS FOR LIFTING MECHANISMS. 4 i

Application filed November 18, 1922. Serial No. 601,936.

To all whom it may concern:

Be it known that I, EDWARD F. DAHILL, a citizen of the United States, and residing at New Bedford, Bristol County, State of Massachusetts, have invented certain new and useful Improvements in Speed-Control Means for Lifting Mechanisms, of which the following is a specification.

This invention relates broadly to means for retarding and controlling the speed of movement of a device or member in opposite direct-ions between fixed limits and in a fixed path where a force acting on said device or member tends to move it quickly, and it may be used to hold said device or member in a selected fixed position between the limits of its movement. It is particularly useful in a device'which is moved upwardly by pistons operated by air under pressure and which descends by gravity; since in that case the movement would normally be quite rapid with the speed increasing until the device reaches its limit of movement thus causing objectionable shock or jar in stopping. In the specific embodiment of the invention-shown for purposes of illustration it is used to control the movements of a ladder pivoted near one end of a vehicle for use in fighting fires and which is elevated to operative position by compressed air operated pistons. The device to which it is applied embodies many features of construction set forth in my Patent No. 983,212 January 31, 1911, but it differs therefrom in the use of compressed air in the cylinders for elevating the ladder and in the control mechanism for retarding the movement. It has been proposed in such cases to use what may be called a dash pot arrangement which acts both ways including a piston cylinder with a piston therein and a projecting piston rod with the ends of the cylinder connected by a restricted passageway, the cylinder and the connection being entirely filled with a liquid such as oil on both sides of the piston and the outer end of the piston rod being so connected to the member which is to be moved as to move with it. This structural arrangement of the retarding means, however, has not been entirely satisfactory. This is because where a piston cylinder and apipe connecting its ends are airtight and filled with liquid such as oil, any upward movement of the piston rod from the cylinder tends to leave a vacant space in the cylinder corresponding in size to that of the part of the rod which has passed out of the cylinder and this interferes with the accuracy, uniformity and efiiciency of the retarding effect.

The embodiment of the present invention shown includes a control cylinder with a piston therein and a projecting piston rod which. is so connected to the ladder to be moved as to move with it with a closed pipe system full of liquid at all times connecting the ends of said cylinder and provided with control valves and consists in a supplemental compensating piston cylinder connected at its upper end to the upper end of said first cylinder through the pipe connection and having its projecting piston rod connected to the piston rod of said controlling cylinder whereby said piston rods will move together and the liquid in the supplemental cylinder will be supplied to the pipe system of the control cylinder as its piston rod moves outward from the cylinder. Tlhediameter of the compensating pistonjcylinder and the diameter of its piston rod are so proportioned with reference to the diameter of the piston. rod of the controlling cylinder that the cubic contents of the. compensating cylinder per linear inch around its piston rodcorresponds exactly to that of the piston rod of the controlling cylinder per linear inch. Since the piston moves upward. in the compensating cylinder as the piston rod of the other cylinder moves out of that cylinderit will be seen that the exact amount of liquid will be positively supplied .from the compensating cylinder to the pipe system of the controlling cylinder as isnecessary to fill the space made vacant by the outward movement of its, piston rod. This structural relation of parts in the retarding device will cause it to operate freely, uniformly and.

accuratelyvin its retarding action throughout its movement in either direction. The novel features will be more fully understood from the following description and claims taken withthe accompanying drawings. I

In the drawings:

Fig. 1 is a vertical side view of the rear end portion of the vehicle having on it the rear endof a ladder with the liftingand retarding mechanism constituting the present invention; i

Fig. 2 is a plan view of what is shown in Figure 1;

Fig. 3 is a side view partly in vertical section of the controlling cylinder and compensating cylinder with their pipe connections;

Fig. 4 is a cross section looking down on the line 4-4 of Figure 3;

Fig. 5 is an enlarged side View partly broken away of one of the compressed air cylinders, the lower part being shown in vertical section; and

Fig. 6 is a vertical section through 'the control valve mechanism for the compressed air passing to the cylinder.

In the drawings the part marked 19 represents the rear end or the supporting portion of the body of a truck such as used in fire departments. A turn table 11 is mounted on roller hearings on this support and is adapted to turn in a horizontal plane to any position or any angle and it carries the ladder and all 01. the mechanism used for raising it and controlling its movement. The ladder 12 is pivotally supported by a cross rod 13 near its end, the said rod 13 in turn being supported by the side brackets 14 connected to the turn table. A compressed air tank 15 has pipe connection through pipe 16 the control valve 17 and pipe 18 to the lower ends of the piston cylinders 19 and 20 as shown in Figure The piston cylinders 19 and 20 are pivotally connected at their lower ends to a fixed rod 21 carried by the turn table, the pivot connection as shown in Figure 5 being in the form of an opening 22 in a downward projection on the lower end of the cylinder. Each cylinder, of course, has its piston 23 as shown in Figure 5, with its piston rod 24 extending through the upper end of the cylinder and the upper end of each of these piston rods is pivotally connected to a rod 25 passing through and secured to the two side bars of the ladder at some distance from its pivot support 13. When the ladder is in horizontal position as shown in Figure 1. these cylinders are preferably at a slight incline from the lower ends inwardly toward the pivot of the ladder. The valve 17 for controlling the supply of compressed air from tank 15 to the cylinders maybe of any of the well known constructions adapted for such use. The form shown in Figure 6 includes a rotary valve member 26 with a central opening and. three lateral openings adapted to connect pipes 16 and 18 or to connect 18 to a vent opening 27. 28 represents a spring stop such as is well known against which the lower end of the ladder makes contact when it reaches its vertical position.

The speed control device constituting the present invention includes a piston cylinder 29 having thesame length as the compressed air piston cylinders 19 and 20 and having its lower end pivoted to the same rod 21 the compressed air cylinders and it is located midway between them. It, of course. includes the piston 30 and its piston rod 31, the upper end of that piston rod being pivotally connected to the above mentioned rod whi h is ca ried by the ladder and to which the piston rods of the compressed air cylinders are pivotally connected. A cylinder of much smaller diameter than cylinder 29 but which has the same length. is supported by cylinder 29 in parallel relation by'a lateral extension 33 on the bot tom of the cylinder 2-9 having a screw threaded socket 314 which it engages. This cylinder has a vent opening 35 at its lower end below any position occupied by its piston 36 for the purpose of admitting and permitting the escape of air in the lower half of the cylinder when the piston moves up and down. The-piston rod 37 extends through the upper end of cylinder 32 and its upper outer end is connected to the outer end of theintegral extension 38 from the collar 39 which connects the piston rod 81 of cylinder 29 to the rod 25 carried by the ladder. This connection is by means of a bifurcated outer end 01 the projection 38 receiving the upper end of the piston rod 37 with the screw threaded bolt 40 passing through that end and the end of the piston rod. The upper surface of the piston 36 is in the same plane as the upper surface of piston 30 in cylinder 29 and because of the above noted connection at the top, the two pistons move up and down together with their upper surfaces always in the same plane. A pipe 41 enters cylinder 29 at its upper end and connects with the vertical pipe 42 which leads downwardly and joins pipe 43 connected to the passage way 44 which in turn opens into the bottom of the cylinder 29 whereby liquid may pass from one end of the cylinder to the other. A. control valve 45 is placed in pipe 42 and also a check valve 46 which permits liquid to pass downwardly through it from the upper part ot the cylinder to the lower part but which will not permit reverse movement. A bypass pipe 47 is connected at its upper end to pipes 41 and 42 at their joint and at its lower end to pipe 43 which leads into the bottom of cylinder 29 through passage way 44 and this by-pass pipe has a control valve 48. It will be observed that this pipe may be used to permit liquid in the bottom portion of cylinder 29 to pass back to the upper end of the cylinder. The compensat ing cylinder 32 is connected at its upper end by pipe 49 to pipe 41 which leads from the upper part of the cylinder 29 through the pipe joint connection 50. It will be observed that the upper portion of the cylinder 32 is in open communication by the above noted pipe connection with the upper end of the control cylinder 29. The cylinder 29 on.

both sides of its piston 30 and all of the pipe connections between its upper and lower end as well as the part of cylinder 32 above its piston and in its pipe connection are completely filled with a liquid such as oil and the pipe system is, course. air and liquid-tight so that during operation the oil is simply circulating from one part of the system to another. it will further be noted from what has been said that the compressed air cylinders and the two control cylinders with their pipe connections are all pivotally mounted as a unit on the rod 2-1 and carried by the turn table and that their upper ends are pivoted to the ladder by rod 25 so that they move as a unit.

When air is turned on and applied to the lower ends of the piston cylinders 19 and 20 and their pistons move upwardly, the piston rods 31 and 37 in the cylinders 29 and32 necessarily move upward at the same rate and at the same time and this upward movement of the piston 30 for instance, in the control cylinder 29 causes the oil to pass through pipes 41. 42 and 43 to the lower end of the cylinder, the valve 48 in pipe 47 being closed at the time. Since the passageway for the oil from the upper to the lower end of the cylinder is restricted, the upward movement of the piston rods in the com pressed air cylinders will be retarded or rendered comparatively slow and the speed of movement can be regulated by the regulating valve 45. During this upward movement of the piston and the passage of the oil from the upper to the lower end of cylinder 29, the upward movement of piston 36 in compensating cylinder 32 will positively force the oil above it to pass through pipe 49 to the connection 50 so as to supplement the oil coming from the upper end of the cylinder 29 sufficiently to prevent the tendency of a vacuum in the lower part of cylinder 29 due to the movement of the rod 31 out of the cylinder. As heretofore indicated the cubic content per linear inch of oil in cylinder 32 above its piston is equal to that of the rod 31 per linear inch and thus the amount of supplemental oil entering the system will correspond exactly to that necessary to take the place of the part of the piston rod 31 which has moved outward and this system will always be completely full of oil with no tendency to a vacuum in any part.

When the ladder reaches the desired elevation under the lifting force of the compressed air cylinders the air may be released and the ladder will be supported by control cylinder 29 through its piston rod 31 since at that time the control valve 48 in the bypass pipe 4'? is closed and the oil in cylinder 29 below its piston can not pass through. pipes 42 and 41 to the cylinder above the piston by reason of check valve 46 and the oil being practically incompressible the piston rod cannot move downward but will be firmly and steadily supported by the oil and will firmly and steadily support the ladder. The ladder, however, may be lowered and its speed oi descent controlled within limits by opening' vali c 48 in by-pass pipe 47 more or less. The downward movement may be arrested at any position by closing valve 48 and the ladder will then be firmly supported in that position. The operation of the coinpensating piston cylinder during the lowering of the ladder is the reverse of that in elevating it since in that case it withdraws surplus oil from the control cylinder system. Although one specific embodiment of the invention has been shown for purposesot illustration, it will be understood that it is not limited beyond what is indicated in the following claims. f

WVhile, in the appended claims, the piston is spoken of as rising and falling, it is obvious that the main cylinder need not be disposed at any particular angle and that the control device will function satisfactorily when arranged horizontally or otherwise. The conduit mentioned in the claims includes any suitable arrangement of piping which may be used to connect the cylinder ends.

Having thus described the inventionwhat isclaimed as new and desired to be secured by Letters Patent is: i

l. A device of the class described for regulating and controlling the speed of motion of a member movable upwardly and downwardly in a fixed path including, a cylinder, a conduit connecting the ends of the cylinder, the cylinder and conduit being filled with liquid, a piston in the cylinder having a piston rod extending through the upper end thereof, the outer end of the piston rod being adapted to be connected to the movable member, means for regulating the passage of fluid through the conduit to control the movement of the piston in both directions, and means for automatically supplying supplemental liquid to the cylinder below the piston as the piston rises and Withdrawing liquid therefrom as the piston falls, said means and the cylinder and conduit constituting together a closed liquid filled system.

2. A device of the class described for regulating and controlling the speed of motion of a member movable upwardly and downwardly in a fixed path including, a cylinder, a conduit connecting the ends of the cylinder, the cylinder and conduit being filled with liquid, a piston in the cylinder having a piston rod extending through the upper end thereof, the outer end of the piston rod being adapted to be connected to'the movable member, means for regulating the passage of fluid through the conduit to control the movement of the piston in both directions, means for automatically supplying supplemental liquid to the cylinder below the piston as the piston rises and withdrawing liquid therefrom as the piston falls, said means including a supplemental cylinder, a piston therein, and connections between the main and supplemental pistons whereby the movement of one is proportional to the movement of the other, said cylinders and conduits constituting together a closed liquid filled system.

3. A device of the class described for regulating and controlling the speed of motion of a member movable upwardly and downwardly in a fixed path including, a cylinder, a conduit connecting the ends of the cylinder, the cylinder and conduit being filled with liquid, a piston in the cylinder having a piston rod extending through the upper end thereof, the outer end of the piston rod being adapted to be connected to the movable member, means for regulating the passage of fluid through the conduit to control the movement of the piston in both directions, means for automatically supplying supplemental liquid to the cylinder below the piston as the piston rises and withdrawing liquid therefrom as the piston falls, said means including a supplemental cylinder, a piston therein, and connections between the main and supplemental pistons whereby said pistons move simultaneously, the cylinders and conduits constituting together a closed liquid filled system.

a. A device of the class described 101 regulating and controlling the speed of motion oi? a member movable upwardly and downwardly in a fixed path including, a main cylinder, a supplemental cylinder parallel thereto, fluid connections between the upper end of each cylinder and the lower end of the main cylinder, pistons in said cylinders, piston rods extending through the upper ends of said cylinders, connections between said piston rods whereby the pistons are constrained to move simultaneously, and means for regulating the flow of fluid passing into or out of the lower end of the main cylinder.

5. A device of the class described for regulating and controlling the speed of motion of a member movable upwardly and clownwardly in a fixed path including, two parallel cylinders, a system of conduits connecting the tops of both cylinders with the bot- 1:

tom of the main cylinder, said system including a conduit having a check valve and a regulating valve therein, and a branch conduit provided with a regulating valve, pistons in said cylinders, piston rods projecting through the tops of said cylinders,

and means connecting said piston rods.

In testimony whereof I hereunto aflix my signature.

EDWARD F. DAHILL. 

